[48] From the first tests
in 1945 through the second series of rocket experiments in 1947,
Aerojet had to use gaseous hydrogen because liquid hydrogen was not
available. Starting in early 1946, Aerojet enlarged its facilities to
handle gaseous hydrogen and oxygen. Gaseous hydrogen under a pressure
of 136 atmospheres was available directly from a trailer of high-
pressure tubes with a capacity of 800 cubic meters (at atmospheric
pressure) and from a stationary bank of high pressure tubes of about
the same capacity. Gaseous oxygen at pressures up to 163 atmospheres
was supplied from two trailers with a capacity of 560 cubic meters.
The total quantity of gases from these sources allowed only a few
minutes of operation-a situation conducive to continued frustrations,
as the following incident illustrates. One day the test crew was
ready to run the rocket and waiting impatiently for a commercial firm
to deliver some needed gas. When it came, the crew quickly connected
the trailer to the pipes leading to the test cell and ran the test.
Meanwhile, the truck driver had gone to the office to get the
delivery ticket validated. On his return he was told the trailer was
empty and could be taken back. Used to leaving such trailers for a
considerable time at other places, the [49] driver simply would
not believe the crew until it was explained rather forcibly to him.
He departed with the trailer, shaking his head.33

By early 1947, the Aerojet group was planning
ahead to the next phase of hydrogen-oxygen experimentation and
acutely felt the handicap of not having a supply of liquid hydrogen.
Envying their former associate, Marvin Stary at Ohio State
University, with his assured supply of liquid hydrogen from the
Johnston liquefier, they decided to attack the problem directly. They
discussed liquid hydrogen with several possible users on the West
Coast and the idea blossomed into a proposed cooperative venture
among several government agencies, universities, and industrial
firms. Confident that they could get liquid hydrogen-and having gone
to as high a thrust as was reasonable with gaseous hydrogen-the
Aerojet engineers proposed to use liquid hydrogen in their third
series of experiments starting in July 1947. They went even further
and proposed to build a flyable rocket engine, complete with its own
controls and turbine-driven pumps. They also recommended that the
government build a medium-scale hydrogen liquefier on the West
Coast.

Aerojet got its new contract in July 1947, but
immediately faced a problem: the cooperative venture to get liquid
hydrogen failed to materialize. Aerojet decided to try to interest
private industry in supplying liquid hydrogen, and if that failed, to
get authority and funding from the Navy to build a liquefier. The
first step was to get an estimate of the amount of liquid hydrogen
needed . The Jet Propulsion Laboratory agreed to participate and
estimated a need for 600-900 kilograms a year. Aerojet added their
needs and settled on a 3600-kilogram total requirement for two years.
Three possible commercial sources were then queried. The Shell
Development Corporation could not supply liquid hydrogen, but had a
surplus of high-purity gaseous hydrogen for sale. The National
Cylinder Gas Company believed that the sale of liquid hydrogen was
neither economical nor safe and recommended liquefaction at the point
of consumption. The Linde Air Products Company submitted an oral bid
for $62 per kilogram at their plant in Los Angeles, but later lowered
the price to $55 per kilogram for the first 1800 kilograms and $44
thereafter.

While soliciting industry, Aerojet began
investigating the possibility of building a liquefier modeled after
Johnston's and estimated that it would cost $100 000, including the
cost of the liquefier, materials, and labor for producing 3630
kilograms of liquid hydrogen. This was half the revised Linde
estimate and had the added advantage of being under Aerojet control
and located near the rocket test stand. Aerojet officials became
enthusiastic over the prospect and set about convincing the Navy. By
late September they received oral approval, which was formalized on
16 December 1947. Aerojet engaged Johnston as a design consultant; he
was also to supply parts of the lique'lier. Herman L. Coplen was the
principal Aerojet engineer for design, construction, and
operation.

Aerojet expected to have the liquefier in
operation by late spring or early summer. As so often happens, the
optimistic schedule fell victim to late equipment deliveries.
However, the liquefier produced its first liquid hydrogen-12
liters-on 3 September 1948. The initial operation turned up the usual
number of bugs; the second operation on 21-23 September produced 120
liters. Of this, 75 liters were shipped to the Jet Propulsion
Laboratory for rocket tests there.

[50] Aerojet was
pleasantly surprised to find that the actual capacity of the
liquefier was 30 liters per hour instead of the design value of 25.
The increased capacity came from a larger hydrogen compressor; the
Johnston-built heat exchangers were oversized. This led Aerojet to
propose, in early 1949, the doubling of the liquefaction capacity by
installing additional hydrogen compressors.

At first, the liquefier was operated
intermittently. Beginning on 8 November, a two-shift operation was
begun to meet the needs of the rocket test engineers, and from 27
December three shifts were employed. By the end of 1948, 7500 liters
(535 kg) of liquid hydrogen had been produced, over 90 percent of it
in November and December. Only about 30 percent of the hydrogen
liquefied was used in test operations; the bulk was lost during
storage and test delays.

In the first three months of operation, the
liquefier was shut down twice, but the troubles were quickly fixed;
the time lost was four days. Overall, the liquefier was highly
successful and made possible the testing of pumps and thrust
chambers.

By the end of March, Coplen had added two more
compressors and the liquefaction rate rose to 80 liters (5.67
kilograms) per hour. But early March had brought catastrophic news to
the liquid hydrogen producers. On 2 March1949,the Bureau of
Aeronautics directed Aerojet to change fuels from liquid hydrogen to
anhydrous hydrazine, which is a liquid at room temperature and
pressure.* The directive allowed Aerojet to continue liquid
hydrogen testing until the end of June, but the irony was that the
switch came just as the producers of liquid hydrogen were finally
prepared to meet rocket test needs.

In its operations through June 1949, the
Aerojet liquefier produced 47 000 liters (3357 kilograms) of liquid
hydrogen at an estimated cost of $29.72 per kilogram. The cost of
commercial gaseous hydrogen and liquid nitrogen were major
expenses.

Sometime after the contract ended in mid-1949,
Aerojet received a government directive to dismantle and prepare the
liquefier for shipment. Very few at Aerojet knew, but the liquefier
was destined for reassembly on a remote Pacific isle for use in the
first test of a thermonuclear device, the predecessor of the hydrogen
bomb.

* The author has been unable to pin down the reason for
this sudden change, but it is not surprising. Hydrazine is storable
and considerably easier to handle than liquid hydrogen, its
performance is high, and interest in it during the 1940s and 1950s
was high. For example, Canright, in his analysis of relative
importance of exhaust velocity and density, preferred hydrazine to
hydrogen even though hydrogen gave higher performance (pp. 47-48) .